Monster recruitment was simplistic in its original inception, being a fixed percentage that could not be changed by the player. If multiple recrutiable monsters appear in the same encounter, only the final felled foe will have a chance to join the Hero.
In the DS and mobile versions, monster allies will only alternate between two lines of dialogue during party chat, as opposed to the fuller conversations of human characters. See the Gallery for recruitment percentages for each monster.

In the original SNES version of VI monster recruitment worked identically to V, though someone in the party must be a Monster Master. When the DS version (and subsequent mobile ports) were produced, this mechanic was retired in favor of "Slime Buddies": slimes players could interact with in towns and dungeons like NPCs who would join the party once certain conditions were met. These slimes are not treated as full characters, however, and thus lack the detailed party chat of humans and Lizzie.

In both versions of the game, any recruited slime may enter into the gladiatorial contests at Slimopolis.

VII is an interesting case; while several monsters can join the heroes, they will never participate in battle. Instead, they will sojourn off to a sort of "wild life reserve" called the Monster Meadows that is unlocked during the normal course of the game. Once there, they can be spoken to in their natural habitat as if they were NPCs, though only one line of dialogue will be spoken. The Animal Magnetism skill makes taming these beasts much easier than in previous games, being the first time a player has direct influence on the probability.

Additionally, defeated monsters will occasionally drop Hearts. These function similarly to the Draconic Diligence and Liquid Metal Mind scrolls from VI and allow the character holding them to take on monster-based vocations at Alltrades Abbey. The main difference is that a character's sprite/model will change into the corresponding monster once the vocation is mastered.

In the 3DS remake, the character will immediately become a monster after using a heart.

In the PS2 version of the game, players will notice several monsters wandering the overworld. These infamous beasties prove much more capable than their randomly encountered counterparts, but once the player pays a visit to Morrie's place they can join the party. This allows the monsters to enter the competition in Morrie's Monstrous Pit, and through the use of the Call team skill they may be summoned into battle for 3 or more turns.

In the 3DS port, all monsters are visible in the overworld, with the infamous monsters being given distinctive icons.